A genetic defect in sex cells may predispose to childhood leukemia

Researchers at the Sainte-Justine University Hospital Center and the University of Montreal have found a possible heredity mechanism that predisposes children to acute lymphoblastic leukemia (ALL), the most common type of blood cancer in children. According to their findings published in Genome Research, the presence of a genetic defect in the egg or sperm that give rise to children with ALL may be a prerequisite for the disease to develop.

A significant number of children with ALL are thought to inherit a rare PRDM9 gene variant responsible for the abnormal sex cells–a gene variant that puts their own children at risk of having ALL-predisposed offspring.

“Our findings indicate ALL susceptibility to be partially hereditary. However, it is not classic heredity in the sense that the abnormal genetic variant does not need to be passed from parent to child for offspring to have the disease,” explains Julie Hussin, a doctoral student in Genomics under the direction of Dr. Philip Awadalla, a genetics researcher.

“Instead, the genetic defect in the egg or sperm from which the children developed is thought to predispose them to leukemia,” continues Julie Hussin. “However, only the children who inherit the genetic variant run the risk of transmitting ALL predispositions to their offspring.” According to the study, more than three quarters of families with affected children have an atypical form of the PRDM9 gene, with half the patients inheriting this genetic variant. The defect is expressed at unusual positions along chromosomes during formation of eggs in females, or sperm in males.